In a road vehicle, especially a car, it is advantageous to be able to freely distribute drive torque to different wheels in order to enhance the driving dynamics of the vehicle. Devices for accomplishing this desired result are in the art referred to as torque vectoring devices.
Torque vectoring devices may be used in either two-wheel drive vehicles or four-wheel drive vehicles, although the latter case must presently be regarded as more common. It can also be used for either rear or front drive shafts or in the cardan shaft for distributing torque between the front and rear drive shafts.
In order to obtain the desired result with regard to the driving dynamics, it may in certain situations be advantageous to provide a drive wheel with a positive torque in relation to the other drive wheel on the driving axle. Such a positive torque may be obtained in a way known per se by a mechanical gear device for gearing-up or increasing the rotational speed of the drive shaft for the wheel in question by for example 10%.
Many examples of such mechanical gear devices are known. In such arrangements being both heavy and expensive, torque vectoring devices are arranged at either side of the central differential for the two drive shafts.
Hence, when a differential rotational speed between two wheels is requested the prior art devices are affecting the rotational speed relative the absolute rotational speed, leading to heavy devices having a relatively high power consumption.